When you're a kid, you're
told that all the stuff around is made of atoms and that
atoms are made of protons and neutrons and electrons. And if you're lucky, you're
told what protons and neutrons are made of. They're made of
three quarks each. But if they're both made
of quarks, how are protons and neutrons different? You're not usually
told this as a kid. And you're not usually
told what quarks are and why they're called
quarks when they're clearly spelled quarks. So protons are made
out of three quarks. That's the first
lie you're told. Protons are not that simple. At any given time, the
proton will have two up quarks with charge plus 2/3,
and a down quark with charge minus 1/3, which of course
all add up to positive 1, because that's the
charge of the proton. These three quarks are
known as valence quarks and they're definitely there. But the proton could
have an additional up quark, anti-up quark pair. An anti-quark is the
anti-particle of a quark. And it could have other
types of quarks-- pairs of strange quarks and
anti-strange quarks, charm quarks, and anti-charm quarks. In fact, the proton
likely has tons of quark, anti-quark pairs. But there is more. The quarks are held together
by the strong force, which is carried by
particles called gluons. So inside the proton, there are
zillions of gluons and quarks all zooming around close
to the speed of light and colliding and annihilating
and new ones are forming and it's a crazy, raging party. Such is the quantum
world in a proton. Wouldn't that violate some
kind of conservation law if particles just
appeared in the proton? Quarks can and do just
appear and disappear, but not out of nothing. Einstein's famous equation,
e equals mc squared means that mass can turn
into a lot of energy or a lot of energy
can turn into mass. In fact, the quarks that
comprise a proton only make of 1% of the total
mass of that proton. That's like saying I drop
some quarters in a bag, and suddenly it
weighs 10 pounds. There's a lot of energy
in all the motion of those crazy, partying
particles-- party-cles. And there's energy
in the gluon field. All of this energy contributes
to the mass of the proton, e equals mc squared. All we need to conserve
is the total mass energy of the proton and
nothing is violated, as quark, anti-quark pairs
pop in and out of existence. But there are a few
other constraints. The total number
of up quarks must be two more than
the anti-up quarks and there must be one more down
quark than anti-down quarks so that the valence quarks
come to a total of three and the quark, anti-quark
pairs of other types must all cancel out, like the
top quark and the charm quark and the strange quark
and the bottom quark. When quark pairs spontaneously
appear in the proton, other properties must be
conserved as well, like charge. So if a quark with charge
positive 2/3 appears, its partner must have
charge negative 2/3. And the spin of the
particles must be opposite, and the colorless of the
proton must be conserved. This is cool. Quarks all have color, except
it's not like real color. Color in quarks is
a type of charge, like the electric
charge, except instead of the electromagnetic
force, it corresponds to the strong force. Quarks can be red, green,
and blue, like the three primary colors of light. And when you mix those
colors, you get white light. So when I said that
protons are colorless, that means that their
three valence quarks must be red, blue, and green. So clever. The quarks can change
color, but the overall color has to stay white. It turns out that the anti-quark
has the opposite color, so that would be like anti-red,
which cancels out red. But I think the most
amazing thing about quarks is that we know all
of this about them without ever directly
detecting one. In fact, you can
never detect just one, because they're
never found alone. The more you separate the
quarks, the more energy you have to put in to
pull the quarks apart. And as you do so, you
eventually put in enough energy to make up the mass of two
new quarks that could then bind to the original two. So next time you're told there
are three quarks in a proton? There are three valence
quarks, and a sea of other quarks-- too many to
count, impossible to count. No, really. We can't take a snapshot. Now, if you want to find
out more about quarks, check on my blog post here on
Ten Quirky Facts About Quarks. And if you want to find
out how big a quark is and how we image tiny things,
like protons and quarks, check out my video
on the smallest things in the universe. Thanks for watching.
That was very well presented. Have an upquark!
Well, now i have a new sub for my youtube.
I wish my teachers had given me a heads-up that everything I was going to be taught was a convenient lie and that I'd spend all my formative years not even realizing how badly I didn't understand the world around me.
I think I would have been less of a smartass.
partycles, heh
That was great. It explained sub-sub-atomic particles better than any other medium through which I've tried to understand the concept.
question, what is the flavor of a quark? or is that another way of saying color?
If only I had seen this video before my physics a level exam...
Funny that they used "quark" as a name for subatomic particles. The German word means rubbish in English.